Me da igual sentarme en la fila de delante o en la de atrás.

Me da igual is a very common Spanish expression meaning something like it’s all the same to me or I don’t mind.

Grammatically:

• me = to me
• da = gives (from dar)
• igual = equal / the same

So the structure is literally closer to it gives the same to me.

The thing that is all the same to you is the action that follows:

• sentarme en la fila de delante o en la de atrás

So the whole sentence is structured like:

• [Me da igual] + [sentarme en...]
• I don’t mind + sitting in...

This is a fixed, everyday expression in Spanish.

Because the verb here is sentarse, not sentar.

• sentar = to seat someone / to sit someone down
• sentarse = to sit down / to take a seat

So if you want to say to sit down / to sit myself, you need the reflexive form:

• sentarme = to sit down / to sit myself

With infinitives in Spanish, reflexive pronouns are attached to the end:

• sentar + me = sentarme
• poner + se = ponerse
• ir + se = irse

So:

• Me da igual sentarme... = I don’t mind sitting...

They are both me, but they do different jobs.

1. me in me da igual

   • This means to me
   • It is the person affected by the expression
   • Example: Me da igual = It’s all the same to me

2. -me in sentarme

   • This belongs to the reflexive verb sentarse
   • It means myself
   • Example: sentarme = to sit myself down / to sit down

So in the sentence:

• Me da igual = I don’t mind
• sentarme = to sit down

They happen to look the same in English-friendly terms, but grammatically they are doing different things.

Because Spanish treats the whole infinitive idea as the subject of dar igual.

The thing that is all the same to me is this whole action:

• sentarme en la fila de delante o en la de atrás

That whole clause is treated as a single idea, so singular da is natural:

• Me da igual [sentarme en la fila de delante o en la de atrás].

Compare:

• Me da igual comer pasta o arroz.
• Me da igual ir hoy o mañana.

Even though there are two alternatives, the sentence is really presenting one overall question of choice, so singular da is standard.

Because de delante here works like the one in front / the front one.

Spanish often uses:

• de delante = in front / at the front
• de atrás = at the back / behind

So:

• la fila de delante = the front row
• la fila de atrás = the back row

You cannot normally say la fila delante in this meaning.

The de is part of the expression. It links the noun to its position:

• el coche de delante = the car in front
• la casa de atrás = the house at the back
• la fila de delante = the row at the front

This is a very common Spanish shortcut.

The full version would be:

• en la fila de delante o en la fila de atrás

But Spanish often avoids repeating a noun when it is obvious. So the second fila is omitted:

• en la fila de delante o en la de atrás

Here, la stands in for la fila:

• la de atrás = the one at the back
• literally, the back one

This is very common in Spanish:

• Prefiero la camisa azul, no la de rayas.
• Quiero el asiento de ventana, no el del pasillo.
• La de atrás = the one at the back

So the omission is natural and sounds more fluent.

Not in this structure.

After a noun like fila, Spanish normally says:

• la fila de delante
• la fila de atrás

You would use delante and detrás by themselves more often in adverbial expressions, for example:

• Siéntate delante. = Sit at the front / Sit in front.
• Está detrás. = It’s behind / It’s at the back.

But when describing which row, Spanish usually uses:

• la fila de delante
• la fila de atrás

Also note that in this sentence it is de atrás, not detrás.
That is normal in noun phrases like this.

Spanish normally uses o for or.

It changes to u only before words that begin with an o sound, to avoid two similar vowel sounds together.

For example:

• siete u ocho
• uno u otro

But here the next word is en, not an o sound, so it stays:

• ...delante o en la de atrás

So o is correct.

Not normally.

The standard expression is:

• Me da igual

This is the natural idiomatic form.
Me es igual is not the usual everyday way to say this in modern Spanish.

Other natural alternatives are:

• No me importa... = I don’t mind...
• Me da lo mismo... = It’s the same to me...
• Me es indiferente... = It’s indifferent to me / I don’t care either way

But for normal conversation, me da igual is one of the most common choices.

Because after expressions like me da igual, Spanish often uses an infinitive to express the action that you do or do not mind.

So:

• Me da igual sentarme...
• literally: Sitting... is all the same to me

This is very similar to English structures like:

• I don’t mind sitting there
• It doesn’t matter to me to sit there

Spanish does this a lot:

• Me da igual ir hoy o mañana.
• Me da igual comer carne o pescado.
• Me da igual esperar.

The infinitive works like a noun-like action: going, eating, waiting, sitting down.

It is very natural in Spain, yes.

In Spain, expressions like these are very common:

• la fila de delante
• la de atrás
• el de arriba
• la de abajo

They are everyday, conversational, and very idiomatic.

In other varieties of Spanish, people may also say things like:

• la fila de adelante
• la fila de atrás
• la fila delantera
• la fila trasera

But for Spanish from Spain, la fila de delante and la de atrás sound completely normal and natural.

Yes. A more expanded version would be:

• Me da igual sentarme en la fila de delante o sentarme en la fila de atrás.

Or:

• Me da igual sentarme en la fila de delante o en la fila de atrás.

Spanish usually shortens this to avoid repetition:

• Me da igual sentarme en la fila de delante o en la de atrás.

That shorter version is the most natural one in normal speech.

A good way to learn this sentence is by chunks:

• me da igual = I don’t mind / it’s all the same to me
• sentarme = to sit down / to sit myself down
• en la fila de delante = in the front row
• en la de atrás = in the back one / in the back row

If you remember those chunks, you can build many similar sentences:

• Me da igual ir en coche o en tren.
• Me da igual comer ahora o más tarde.
• Me da igual sentarme delante o detrás.

That is often more useful than trying to translate word by word.